Among electrochemical devices, such as electric double-layer capacitors, lithium ion capacitors, redox capacitors, lithium ion batteries and the like, there exists one which is provided with a structure in which at least a pair of terminals is led out of a package where an electric storage element is sealed.
For example, an electric double-layer capacitor as mentioned above is provided with a structure in which an electric storage element which is composed of positive electrodes and negative electrodes stacked in sequence with separators being interposed therebetween, one end of a positive terminal which is electrically connected to the positive electrodes of the electric storage element, one end of a negative terminal which is electrically connected to the negative electrodes of the electric storage element, and an electrolyte solution are sealed in a package, while the other end of the positive terminal and the other end of the negative terminal are led out of the package. The package is formed of a laminated film having, for example, a plastic protective layer, a metal barrier layer and a plastic heat seal layer in sequence. The package is formed, for example, by bending and folding over a sheet of rectangular film of a predetermined size, and then heat sealing the three sides thereof (at the overlaid portion of the heat seal layer).
As recent electrochemical devices including the above exemplified electric double-layer capacitor have been reduced in size, the electrochemical devices are desired to be mounted on a substrate or the like with high-temperature reflow soldering using lead-free solder, in the same manner as general electronic components are mounted. In other words, the need for electrochemical devices which are compatible with high-temperature reflow soldering using lead-free solder has increased.
However, the conventional electrochemical devices are not compatible with high-temperature reflow soldering using lead-free solder, therefore it is difficult to meet the need for mounting the electrochemical devices on a substrate or the like with high-temperature reflow soldering using lead-free solder, in the same manner as general electronic components are mounted.
The furnace temperature in a reflow furnace used for reflow soldering using lead-free solder reaches a maximum of approximately 250° C., for example. As a result, when a conventional electrochemical device is placed in the reflow furnace to perform reflow soldering, heat flows through and enters the package which is directly exposed to a furnace atmosphere of the reflow furnace. Then, heat may cause a failure such as heat-deterioration of the electric storage element in the package, and significant reduction of the electrical properties of the electrochemical device or the like.
Patent Document 1 discloses a structure in which an electrochemical device is housed in a casing; however, the casing is not adapted to actively suppress heat from being transferred to the package, therefore a failure similar to that described above may occur.    Patent Document 1: Japanese Patent Laid-open No. 2000-286171